Pot-caught Brown Crab

Pot-caught Brown Crab
Dr Tom Pickerell
National Shellfish Development Manager
Shellfish Association of Great Britain
Presentation Outline
• The animal
• The fishery
• What is ‘sustainability’?
• How sustainable is pot-caught brown crab?
1
The Animal
Brown (or Edible) Crab (Cancer pagurus)
The Animal
Brown (or Edible) Crab (Cancer pagurus)
2
The Animal
Dressed Crab
The Animal
• Grow by casting (moulting) their shell, and then
hardening a new shell at a slightly larger size.
• Mature around 120-130mm carapace width
• Mating occurs while the female shell is soft.
• After spawning (late summer or autumn) eggs
carried by the female under the abdomen
• Hatch in early summer, planktonic larvae settle in
summer or autumn.
• Tagging studies show brown crabs may move up to
a few kms a day, and over 100 kms over months
3
The Fishery
• Brown crabs are widely distributed on soft, gravely
and stony habitats.
• The main stocks occur along the north east coast,
in the Channel, and along the Welsh coast and
West of Scotland.
• Landings come from traditional inshore fisheries
plus specialist offshore fisheries off the Humber,
West of Scotland, the outer Wash, and in the
western mid-Channel.
• Landed around the UK, but the main sources are
the east coast, and the south coast and West of
Scotland.
The Fishery
• Brown crabs are caught by creels, parlour pots and
inkwell pots
4
The Fishery
• Historically a small-scale inshore fishery
• Offshore grounds targeted later
• Classed as a principal capture species (scallop,
lobster, cockle, and Nephrops)
• 21% total volume shellfish landed*
• 26,000 tonnes in 2006*
• Landings worth £34m*
*UK vessels landing in UK
What is ‘sustainability’?
• Stock-size sustainability
• Ecosystem sustainability
• Global sustainability
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What is ‘sustainability’?
• Stock-size sustainability
• Ecosystem sustainability
• Global sustainability
Stock-size sustainability
• Based on proportion of the fishery taken from the
stock each ‘season’
• A ‘sustainable’ fishery in this example would
harvest equal/less than the recruitment the
following season*
• Maximum Sustainable Yield (MSY)
• Roughly 30% of stock in general
• Need accurate science – Orange roughy in NZ
* Need to take into account natural mortality
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Stock-size sustainability
Stock-size sustainability
7
Stock-size sustainability
Stock-size sustainability
8
Stock-size sustainability
Stock-size sustainability - UNDERFISHING
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Stock-size sustainability - OVERFISHING
Stock-size sustainability
• Unlike most TAC species there is no ICES survey
• Fishing effort data are collected by Defra
• CEFAS collects data from fishers log books
• The Northumberland, North Eastern, Cornwall and
South Wales SFCs collect permit scheme data on
crab potting effort.
• Crab stocks are assessed by analysing the size
distribution of crab landed from the fisheries, with
the aid of growth rate data obtained from tagging in
the 1970s.
10
Stock-size sustainability
• “The Channel and North Sea stocks are fully
exploited, but the spawning stock still appears to be
robust, and there is no sign that the recruitment of
small crab has declined” (Bannister, 2004)
• “Fishing mortality is moderate on males, but fairly
high on females, but appears to have fallen slightly
since the 1980's” (Bannister, 2004)
Stock-size sustainability
• The shellfish licensing scheme caps the numbers of
vessels allowed to fish for crustaceans
• It does not limit the number of pots that can be set
• If the number of pots used by individuals increases
steadily it will causes fishing mortality to increase
and will reduce sustainability.
• The industry itself is calling for a cap on pot
numbers to ensure sustainability and a viable
fishery.
11
What is ‘sustainability’?
• Stock-size sustainability
• Ecosystem sustainability
• Global sustainability
Ecosystem sustainability
• Looks at the bigger-picture; not just the stock in
question
• The wider impacts of the fishery:
– Bycatch
– Habitat damage
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Ecosystem sustainability
Ecosystem sustainability
13
Ecosystem sustainability
Ecosystem sustainability
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Ecosystem sustainability
Ecosystem sustainability
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Ecosystem sustainability - bycatch
• Bullimore, B.A., Newman, P.B., Kaiser, MJ.,
Gilbert, S.E. & Lock, K.M., (2001). A study of
catches in a fleet of 'ghost-fishing' pots. Fishery
Bulletin, 99, 247-253.
Ecosystem sustainability - bycatch
• “Spider and brown crabs dominated the catches,
whereas lobster, velvet swimming crab, and fishes
were caught less frequently.”
• “Divers found several spider crabs that had been
tagged in one pot, but on the subsequent sampling
occasion, they were recorded in a different pot.
These animals had escaped one trap only to be
captured in another.”
16
Ecosystem sustainability – habitat damage
• Eno N.C., MacDonald D.S. & Amos S.C. (1996). A
study on the effects of fish (crustacea/mollusc)
traps on benthic habitats and species. Report to the
European Commission.
Ecosystem sustainability – habitat damage
• “One month’s active fishing using crab and lobster
pots caused no difference in abundance of species
between control and experimental study plots.”
• “Abundance of some species increased after
potting in comparison with their abundance before
potting.”
• “Potting did not have a detrimental effect on the
abundance of species studied.”
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Ecosystem sustainability
• MCS “FISHING METHODS LEAGUE TABLE”
• Overview of 24 fishing methods
• Scored the impact of crab pots as:
What is ‘sustainability’?
• Stock-size sustainability
• Ecosystem sustainability
• Global sustainability
18
Global sustainability
• Concerned with the ‘life-cycle’ of the product
– Transport
– Packaging
– Waste etc
Global sustainability
19
Global sustainability
Global sustainability
Food Miles
Packaging
Waste
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Global sustainability
Global sustainability
• Food miles issue not well studied
• Most UK shellfish has little packaging
• Or it’s own shell! – biodegradable waste
• Brown crabs processed in UK or shipped live to the
markets in France & Spain
• Not shelled in Far East unlike some other species
21
What is ‘sustainability’?
• Stock-size sustainability
• Ecosystem sustainability
• Global sustainability
What do others think?
“Choose crabs that have been caught in pots, the
most sustainable method of fishing for crabs.”
“Examples of seafood from well managed fisheries:
Pot caught Brown crab from Devon”
“crabs are caught in traps that take little bycatch”
22
Take-home Messages (I)
• Look beyond just stock-size and proportion
harvested
• Consider wider ecosystem effects of the fishing
method
• Think about the global impact of the finished
product
Take-home Messages (II)
• “The Channel and North Sea stocks are fully
exploited, but the spawning stock still appears to be
robust”
• “There is no sign that the recruitment of small crab
has declined”
• Potting is a low impact method of fishing
• Potting has little bycatch
• Industry wants effort cap to sustain the fishery
• The product remains in UK or landed/shipped live
to Continent
23
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